94. Das somatosensorische Nervensystem: Rezeptoren

Charakterisieren Sie die somatosensorischen Rezeptoren anhand ihrer 1.

Modalitat (Mechano-,Thermo-,Nozizeptoren), 2. Quelle des Stimulus

(Extero-,Proprio-,Interozeptoren) und 3. histologischen Struktur

(korpuskulare Nervenendigungen, freie Nervenendigungen). Beschreiben

Sie die Mechanorezeptoren der Haut und ihre Funktionen: Vater-Pacini-

Korperchen, Meissner-Korperchen, Ruffini-Korperchen, Merkel-

Korperchen, freie Nervenendigungen.

Was ist ein Dermatom? Erklaren Sie wie diese am Kopf und Korper

verteilt sind.

Erlautern Sie die Grundlage der somatosensorischen rezeptiven Felder.

Inwiefern steht das Konzept des Dermatomes mit diesen rezeptiven

Feldern in Zusammenhang?

Definieren Sie die Termini Rezeptorsensitivitat, Rezeptorspezifizitat und

rezeptives Feld. Erklaren Sie inwiefern die Dichte der peripheren

Innervation mit der Große des rezeptiven Feldes korreliert.

Definieren Sie schnelle und langsame Adaptation der sensorischen

Rezeption.

95. Das somatosensorische Nervensystem: die Hinterstrangbahn

Beschreiben Sie die Untergruppen der somatischen Sensibilitat, welche durch das

lemniskale System bedient werden.

Listen Sie die Anteile des lemniskalen Systems und ihre trigeminalen Analoga auf.

Erklaren Sie die funktionellen Bestandteile des lemniskalen Systems.

Erlautern Sie die topographische Representation des Korpers in Hohe der Kerne im

Hinterstrang, im ventrobasalen Thalamus und im somatosensorischen Kortex.

Was ist die Zwei-Punkt-Diskrimination? Erlautern Sie wie diese mit der peripheren

Innervationsdichte und der Große des rezeptiven Feldes zusammenhangt.

Nennen Sie die Faktoren, welche fur die sehr hohe Tastscharfe der Hande und des

Gesichtes verantwortlich sind.

Was sind die Anzeichen und Symptome einer Dysfunktion des lemniskalen Systems?

Wie wird durch die laterale Hemmung die Zwei-Punkt-Diskrimination verbessert?

Erklaren Sie wie sich die Dichte der peripheren Innervation, in der Große des

respektiven reprasentierenden Feldes im Gyrus postcentralis widerspiegelt.

Was ist mit feinem Tastsinn gemeint? Nennen Sie die einzelnen Nerven und

Verbindungen, von der Peripherie bis zur Hirnrinde.

Das somatosensorische Nervensystem

Sehen

Gehor

Gefuhl

(Tastsinn)

Geschmack

Riechen

Aristoteles:

Die funf Sinne

:

THEORIEN ÜBER DIE FUNKTION

DES SOMATOSENSORISCHEN SYSTEMS

SPEZIFICITĀTSTHEORIE

THEORIE VON HENRY HEAD

”PATTERN” THEORIE

Gesetz der spezifischen Sinnesenergien

PHOSPHENE

Punktförmige Repräsentation der Rezeptoren/sensorisches Mosaik

Sir Henry Head (1861 to 1940)

Sir Henry Head's experiments increased our understanding of

the sensory system and enhanced our ability to examine

it.[5,37-41] Frustrated with the inconsistent reports of

patients with sensory loss, he performed his most famous

experiment in which he severed his own radial nerve and

documented the return of sensory modalities.[5,42] This

experiment, however, was not his major contribution to our

understanding of the sensory examination. After years of

experiments on sensory nerves, Head began to piece together

a possible organization for the sensory afferent system. He

divided the peripheral nervous system into three distinct

sensibilities: deep, protopathic, and epicritic. He described

deep sensibility as being served by fibers that ran mainly with

muscular nerves. They were concerned with pressure stimuli

as well as with joints, tendons, and muscle movement.

Protopathic sensibility was described as that which was

"capable of responding to painful cutaneous stimuli and

extremes of heat and cold."[5] Protopathic pain was

generated in the posterior nerve root and exhibited the highest

threshold for a pain response with poor localization, failure to

adapt, and intense response to stimulation. Epicritic

sensibility was the ability to discriminate between two

points and to recognize fine grades in temperature change.

Head believed it was more precisely tuned than protopathic

sensation. Head correctly surmised that epicritic pain fibers

were distributed throughout the peripheral nervous system and

had slower regeneration times.[5,43-45] Henry HEAD

1861-1940

HENRY HEAD:

PROTOPATHISCHE,

EPIKRITISCHE und

TIEFSENSIBILITÄT

In einem Selbstversuch untersuchte Head

die Ruckkehr der Sensibilitat der Haut

nach Durschneiden des n. cutaneus

antebrachii lateralis.

ÜBERTRAGENER

SCHMERZ REFERRED PAIN

A

[Head zones]

(Invest Opbthahnol Vis

Sd. 1999;4O:513-519)

Corneal sensations result from the activation of sensory

nerve afferents, which are the peripheral branches of various

types of trigeminal nociceptive neurons. In the cat's eye, some

of the corneal sensory nerve fibers (approximately 20%) are

activated only by mechanical forces and are called mechanosensory.

The majority of corneal nerve fibers (approximately

70%) also respond to chemical irritants and to noxious heat

and thus are classified as polymodal nociceptive fibers. Finally,

a small group (approximately 10%) respond preferentially to

cooling of the corneal surface and are called "cold" fibers (for

review see Ref. 6).

Innervation der Cornea:

nur C-Fasern

Humán cornea szenzitivitás

(Invest Ophthalmol Vis Sci. 2001;42:2063–2067)

METHYLÉNKÉK

VITÁLFESTÉS Hasonló morfológiájú, de funkcionálisan különböző receptorok.

identified in more than 70% of the cases. The incidence ofcorrect identification was slightly lower for heat stimuli.Mechanical stimuli were confounded with other types ofstimuli in about half of the trials.

Correlation between sensation parameters and single-fibre activity

Table 2 compares the stimulus intensities necessary toexcite primary corneal sensory units in the cat (firing

M. C. Acosta, C. Belmonte and J. Gallar520 J. Physiol. 534.2

Table 1. Percentage of correct identification of the stimulus modality applied to the humancornea

Stimulus reported

Stimulus No stimulusapplied Mechanical Chemical Heat Cold or undefined

Mechanical 47 ± 7% 17± 7% 17± 8% 19± 9% 0%Chemical 8± 4% 75 ± 7% 17± 7% 0% 0%Heat 3± 3% 31± 9% 64 ± 9% 0% 3± 3%Cold 11± 7% 17± 7% 0% 72 ± 10% 0%Sham 0% 6± 6% 6± 6% 0% 88 ± 7%

Data are means± S.E.M. of the percentage of correct identifications determined in 9 subjects.

Table 2. Sensation threshold in human and firing threshold of corneal units in the cat

Human Cat

Stimulus Sensation Polymodal Cold-sensitiveapplied threshold Mechanosensory units units

Mechanical (ml min_1) 79± 5 109± 24(23%) 79± 9(60%) 62± 8(25%)Chemical (%CO2) 21± 3 (3%)† 34± 3 (54%) 21± 4 (80%)Heat (°C) +1.2± 0.2 (4%)† +2± 0 (36%) (_60%)*Cold (°C) _2.4± 0.4 (4%)† _2.7± 0.8 (9%) _1± 0 (100%)

Data are means± S.E.M. Percentage of corneal sensory units recruited by each type of stimulation is alsoshown in parentheses. Data correspond to units that changed their basal firing frequency by more than30% in response to at least one-third of the pulses of each modality.* Percentage of units that reducedtheir firing discharge during application of heat stimuli. †For values below 5% thresholds were notcalculated.

Figure8. Correlation between VAS ratings in humansand impulse response of corneal units in cats

A, mechanical stimulation. B, cold stimulation. Data wereobtained using an identical stimulation protocol for thepsychophysical and the electrophysiological experiments.Pearson’s correlation and linear regression (continuouslines) were statistically significant.

(Journal of Physiology (2001), 534.2, pp.511–525)

NAFE (1934): “PATTERN” THEORIE”

Lele, Weddel: Untersuchungen an der corneale Sensibilitat:

identische Morphologie – unterschiedliche Funktion

ARANYKLORID

IMPREGNATIO

Sensations evoked in the cornea by selective mechanical, chemical, heat

and cold stimulation always presented an irritation component

MECHANOREZEPTION (TASTSINN)

[Asphyxie, Kaltblock, Kokain]

Tastsinn

Schwelle: 5-10 mg/10m

Rezeptivfelder: mm2-cm2

Zweipunktschwelle 0,9 - 40 mm

Innervationsdichte

Orientierung

Applikation der Reize:

simultan < nacheinander

Rezeptive Felder: mm2-cm2

Zwei-Punkt-Schwelle:

Rucken: 40 cm, Hand 20 cm,

Fingerspitze, Zunge: 1-3 mm

˃

Pacini

Ruffini

Meissner

Merkel

Räumliches Auflösungsvermögen und Innervationsdichte

Braille : 600/min (100 Worter)

Ereignis-korrelierte Potenziale

NEUROLOGY 2000;54:2230–2236

Superior tactile spatial acuity in blind Braille readers

Propriozeption

Tiefsensibilität, kinaesthetische Sensibilität

Stellungssinn - Bewegungssinn - Kraftsinn

- Muskelafferenzen - Muskelspindeln

McCloskey - Dehnung durchgeschnittener Sehnen erzeugt

Illusionen von Gelenkbewegungen

- Mechanosensoren in den Gelenkkapseln (Ruffini)

- Hautrezeptoren

- Mechanosensoren der Sehnen

- Visuelle u. vestibulaere Informationen

Syphilis

Tabes dorsalis

Haptische Wahrnehmung

Wahrnehmung durch aktive Exploration im Unterschied zur taktilen

Wahrnehmung, bei der das wahrnehmende Subjekt passiv beruhrt wird.

Überstreichen der Oberflache

Drucken

Konturen nachfahren

Umfassen

Gewicht-

Schatzung

tasten

Temperatur

Explorationsstrategien zur

Objekterkennung:

Hinterstrangsystem (Lemniscus medialis)

Dermatom

Somatotopie

Modalitaetsspezifizitaet einzelner Neuronen ist erhalten

(Hinterstrangkernen, Thalamus, Kortex)

Laterale Hemmung - Kontrastverschaerfung

Kleine rezeptive Felder (distal kleiner)

Laterale Hemmung - Kontrastverschaerfung

Eigenschaften der lemniscalen VB Neurone:

Somatotopie

Kleine, kontralateral gelegene (gekreuzter Eingang)

rezeptive Felder mit Zentrum-Umfeld Organisation

Modalitats-spezifisch, Eingang nur von einem Rezeptortyp

(Druck, Beruhrung, Glenkstellung)

Eingange von Hinterstrang Kernen

Projektion nur zu SI und SII

François Magendie

(1783-1855)

Sir Charles Bell Bell-Magendie Gesetz

Syphilis

Tabes dorsalis

KAHLER-

REGEL

LEMNISCUS

MEDIALIS

LEMNISCUS

TRIGEMINALIS

Die Verarbeitung mechanorezeptiver Information im ZNS

LEMNISCUS MEDIALIS und LEMNISCUS TRIGEMINALIS

Dermatom (griech. derma „Haut“, tomus „Schnitt“):

das von einem Ruckenmarksnerven (Spinalnerven)

innervierte segmentale Hautgebiet.

Methode zur Bestimmung des Dermatoms:

* antidrome Vasodilatation

* Herpes Zoster (Gurtelrose)

* Denervation/Schadigung einzelner Hinterwurzel (”spared root”)

("ersparte Wurzel")

DERMATOM

segmentale Hautgebiet innerviert

von einer Hinterwurzel

peripheres

Nerv

Hinterwurzel

HERPES ZOSTER BEGRENZT AUF EINEM

DERMATOM

UNEMPFINDLICHE HAUTGEBIETE NACH

DORSALER RHIZOTOMIE

Dermatom: klinische Bedeutung : topographische Diagnose

C2

“Diskushernie”

Dermatom: klinische Bedeutung : topographische Diagnose

herpes zoster

übertragener

Schmerz

LATERALE HEMMUNG

Kontrastverscharfung

LATERALE HEMMUNG

Zwei-Punkt-

Diskrimination

exakte

Lokalisation

Kante

KORTIKALE LOKALISATION

FRENOLOGIE, [1825]

Franz Joseph GALL, (1758–1828)

J. C. Spurzheim (1776–1832)

Korbinian Brodmann

1868-1918

Paul Broca

1824-1880

Wilder Penfield

1891-1976

Carl Wernicke

1848-1904

Pierre Paul BROCA

Motorische Sprachregion, 1861:

„Nous parlons avec l’hemisphere gauche”

Broca-Areal: Area 44, 45

(motorische Aphasie)

Karl WERNICKE, 1867

Sensorische Sprachregion

Wernicke-regió: Areal 22

(sensorische Aphasie)

Korbinian BRODMANN, 1909

Zytoarchitektonischer Aufbau der Grosshirnrinde: 52 Areale

PET-AUDIO PET-VISUAL

First functional map of the human

cerebral cortex, outlining the areas of

the brain which produce movements

and auras. (Foerster & Penfield, 1930)

Sketch of a patient's brain, annotated throughout the

operation, to show the areas of motor and

somatosensory cortices which elicit movements of, or

sensations in, the mouth and lips. (Penfield &

Boldrey, 1937).

PENFIELD IN SHERRINGTON’S

LABORATÓRIUM IN LONDON

(operiert von

Herbert Olivecrona,

1936)

Wilder Penfield:

Kortikale Lokalisation

Reise um meinem Schadel

The first patient’s-eye-view

account of a brain operation in

medical history…remarkable.

— Time

[Karinthy] possesses the sharp

and biting satire of Voltaire; the

provocative doubt of Shaw; the

poetic fantasy of Maeterlinck.

Karinthy is a universal literary

genius: playwright, humorist,

poet, novelist, critic, essayist,

literary caricaturist, etc…He has

that rare ability of our own

Charlie Chaplin, in that whatever

he attempts to do, he can make

us feel that he is a genius.

— Los Angeles Times

The distinguished Hungarian author Frigyes Karinthy

was sitting in a Budapest café, wondering whether to

write a long-planned monograph on modern man or a

new play, when he was disturbed by the roaring—so

loud as to drown out all other noises—of a passing

train. Soon it was gone, only to be succeeded by

another. And another. Strange, Karinthy thought, it

had been years since Budapest had streetcars. Only

then did he realize he was suffering from an auditory

hallucination of extraordinary intensity.

What in fact Karinthy was suffering from was a brain

tumor, not cancerous but hardly benign, though it

was only much later—after spells of giddiness,

fainting fits, friends remarking that his handwriting

had altered, and books going blank before his eyes—

that he consulted a doctor and embarked on a series

of examinations that would lead to brain surgery.

Karinthy’s description of his descent into illness and

his observations of his symptoms, thoughts, and

feelings, as well as of his friends’ and doctors’ varied

responses to his predicament, are exact and

engrossing and entirely free of self-pity. A Journey

Round My Skull is not only an extraordinary piece of

medical testimony, but a powerful work of

literature—one that dances brilliantly on the edge of

extinction.

DIE GRÖSSE DER KORTIKALEN REPRESENTATION IST

DER REZEPTORENDICHTE ABHĀNGIG

Kortikale Representation

SENSORISCHER

HOMUNCULUS

Homonculus vs Hermunculus

Models of sensory and

motor homunculi at the

Natural History Museum

in London.

Somatotopie

medio-lateral

Modalität

antero-posterior

S I - kontralateral

S II - kontralateral u. ipsilateral

Area 3a - Muskelspindelrezeptoren

Area 3b - SA Mechanorezeptor

Area 1 - RA Mechanorezeptor

Area 2 - Gelenke, Periosteum, Fasciae

DER KOLUMNARE AUFBAU DES

SOMATOSENSORISCHEN CORTEX

Area 3a, 3b:

receptorspecifsche Neurone

Area 1, 2:

komplex Neurone

(ergreifen eines Objektes,

Bewegung auf der Hautoberflaeche)

Mountcastle, Brain (1997), 120, 701–722

ENTDECKUNG DES KOLUMNAREN AUFBAUS DES

SOMATOSENSORISCHEN CORTEX (1955)

Vernon B. Mountcastle (1918-)

The Brain Voyager , "the Jacques Cousteau of the cortex."

More than a half-century has passed, but revered neuroscientist Vernon Mountcastle

recalls his most celebrated moment of discovery with perfect precision. It was when he

determined that the brain, unlike any other part of the human body, is divided into

magnificent little subunits—or columns—each with its own specific role.

On that day in 1955, Mountcastle—who received his M.D. from the School of

Medicine in 1942 and went on to direct physiology from 1964 to 1980—was studying

the results of tests on the brains of cats, recording the character of each cell from

successive penetration layers. “I was writing them down vertically on a yellow piece

of paper,” he recalls. Suddenly the vertical notetaking helped him see the stunning

pattern in the brain: Skin cells lay atop skin cells, joint cells atop joint cells and so

on, extending in columns from the brain’s surface all the way down through six

layers of cortex. “That was my ‘aha’ experience,” he says.

Mountcastle’s revelations forever changed his field: Before his breakthrough,

researchers had believed that brain cells were organized randomly, with each layer of

the cortex having a specific function.

David Hubel in his Nobel Prize acceptance speech said

Mountcastle's "discovery of columns in the somatosensory

cortex was surely the single most important contribution to

the understanding of cerebral cortex since Ramón y Cajal.”

Jeff Hawkins in his book On Intelligence describes

Mountcastle's 1978 article, An organizing principle..., as "the

rosetta stone of neuroscience”.

[Mountcastle, V. B. (1978), "An Organizing Principle for

Cerebral Function: The Unit Model and the Distributed

System”]

Somatotopie: Hinterstrangskerne

und Thalamus

Plastizitaet im somatosensorischen Cortex nach

der Amputation des dritten Fingers

Mikrostimulation kutaner rezeptiver Felder mit vibro-tactilen Reizen

Kortikale Aktivation durch Mikrostimulation kutaner rezeptiver Felder mit vibro-tactilen Reizen:

fMRI-Untersuchungen (Funktionelle Magnetresonanztomographie)

Kortikale Aktivation infolge der Stimulation kutaner rezeptiver Felder

mit vibro-tactilen Reizen: fMRI-Untersuchungen

Journal of Neurophysiology 80, 1998, 1533-1546

Karen D. Davis1, 3, Chun L. Kwan1, 3, Adrian P. Crawley2, and David J. Mikulis2, 3

THALAMUS S II

SII

VPL S2

VPL

Kortexlaesionen SI: Erkenntniss von Form und Gestalt gestört

Kugel: Differenzlimen: intakt: 1.1 mm

laediert: 12 mm

Kugel vs Ellipsoid: intakt: 28 mm vs 27.5 x 30

laediert: 21 x 50 mm!

Schaedigung des Zwei-Punkt-Diskriminationsvermögens

Astereognosie (Tastblindheit)

Störungen der Vibrationssensibilitaet

verminderter Tastsinn

Schmerz- u. Temperatursinn bleiben intakt

Brodmann Area 5: Parietaler Assoziationscortex:

Störungen der Stereognosie